Five new cases of E coli have been detected in an outbreak linked to the children's farm in Surrey where 45 people were taken ill after visiting over the summer.

Of the 45 affected, 12 are children being treated in hospital. Four of them remain seriously ill.

Six children are in a stable condition, and two were described as "improving" by the Health Protection Agency (HPA).

Godstone Farm in Surrey closed its doors to the public last Saturday in light of the outbreak.

Horton Park Children's Farm in Epsom, Surrey, its sister farm, has also shut because of "unsatisfactory" hygiene arrangements.

Horton Park is run by the same company that operates Godstone Farm outside Redhill, where youngsters are also encouraged to stroke and feed tame animals such as goats, rabbits and piglets.

The bacteria usually causes severe diarrhoea but can occasionally trigger kidney and blood complications. The UK's most lethal recent outbreak killed 21 people in Lanarkshire, Scotland, in 1996.

An HPA spokeswoman said it was not aware of any cases of E coli at Horton Park, but added: "The hygiene arrangements were found to be unsatisfactory and the HPA advised the local authority that the farm should be closed immediately while these defects were rectified."

Justin McCracken, head of the HPA, has apologised to the parents of the ill children for the handling of the situation and the delays in closing down Godstone Farm.

A spokeswoman for Horton Park said the farm was closed voluntarily because of the perceived "slight risk" of more children contracting E coli.

Sign up for the Guardian Today

Our editors' picks for the day's top news and commentary delivered to your inbox each morning.